Problem: $ { \left[\begin{array}{rr}{4} & {2} \\ {-2} & {3} \\ {-1} & {0}\end{array}\right]+\left[\begin{array}{rr}{0} & {0} \\ {0} & {2} \\ {1} & {-1}\end{array}\right] = {?} } $
Solution: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rr}{4}+{0} & {2}+{0} \\ {-2}+{0} & {3}+{2} \\ {-1}+{1} & {0}+{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{4} & {2} \\ {-2} & {5} \\ {0} & {-1}\end{array}\right]}$